This invention relates to improvements in a self-restoring type current limiting device.
The self-restoring type of current limiting devices includes an amount of a self-restoring type current limiting material put in the form of a solid electrically conductive at room temperature and responsive to a flow of overcurrent therethrough to be evaporated to limit the overcurrent. After the current has been limited, the evaporated material is rapidly self-restored to its original good electrically conductive state.
In current limiting devices of the type referred to, the current limiting operation thereof is determined by the cross sectional area of the narrowest portion of the current passageway where the current limiting material is first evaporated. The performance of current limitation can be improved by making a cross sectional area of that portion of the current passageway where the current limiting material is first evaporated as small as possible. This measure however, results in a decrease in magnitude of a current normally flowing through the current passageway. Therefore current limiting devices of the type referred to are required to include the current passageway having its minimum cross sectional area as small as possible while a current normally flowing through the current passageway is high in magnitude.